A new stapling technique uses hexafluorobenzene to link two segments of this peptide.

Credit: Adapted from J. Am. Chem. Soc.

A new stapling technique uses hexafluorobenzene to link two segments of this peptide.

Credit: Adapted from J. Am. Chem. Soc.

When chemists say they’re stapling a peptide, what they’re actually doing is cross-linking some of the amino acid side chains to make the peptide more stable or to adjust its properties. MIT’s Bradley L. Pentelute, Tufts University’s Yu-Shan Lin, and coworkers have developed a new stapling technique that could complement established methods (J. Am. Chem. Soc., DOI: 10.1021/ja400119t). The researchers originally planned to develop a mild way to arylate a cysteine thiol, and they were adapting a known reaction between thiols and hexafluorobenzene for that purpose. But two cysteines consistently added to the benzene species instead of one, so they decided to focus on cross-linking instead. Stapling traditionally calls for nonnatural amino acids and a metal catalyst, but the new technique doesn’t require them. It is compatible with protein synthesis techniques, as the team demonstrated by building a stabilized three-helix protein that binds to a breast cancer biomarker.